1. Field of the Invention
The present invention relates to improvements in semiconductor switch devices, and more particularly to improvements in semiconductor switch device using transistor wherein a secondary output of a current transformer which responds to a main current is supplied as a control electrode current.
2. Description of the Prior Art
In semiconductor switches, there has been a growing interest in the development of simplified means for supplying and controlling the control electrode current. In practice, such control current, if considerably large, can hardly be isolated and on-off controlled. To do this, prior art techniques have had to use a control electrode power source capable of isolated power supply for each switch unit, which has necessitated transformers and rectifiers of large capacity. When a large control electrode current is necessary to cope with a maximum main current, the power source must be large enough to deal with such current.